For permitting to finish a work gear by sliding a table, supporting the gear, horizontally under a condition where the work gear is engaged with a gear-finishing tool such as shaving cutter from a diagonal direction, table assembly of a conventional gear finishing machine is fashioned as shown, for example, in Japanese Patent Publication No. 54-21036, to include not only a sliding table, mounted slidably leftwards and rightwards of the machine and driven to slide by a feed motor, but a rotatable table supported rotatably about a vertical axis or center of the machine.
Such rotatable table is fashioned to be clamped to the sliding table or to a knee portion of the machine by a releaseable clamp means and, prior to a gear finishing operation, it is oriented or rotated at an .unclamped condition thereof to a required angular position using a table rotating means and, then, is re-clamped.
As well known, this kind of table mechanism which permits to slide a work table diagonally by a combination of a sliding table and rotatable table requires a parallel link mechanism for securing a parallelism of the rotatable table relative to the sliding table so as to assure a horizontal stability of the whole of table assembly (see, for example, Japanese Patent Publication No.27-5197-) . Because of an accuracy required, such parallel link mechanism is quite expensive.
For eliminating the parallel link mechanism, a structure is considered in that combination of a pair of sliding tables, one of which is slidable leftwards and rightwards of a gear finishing machine and the other of which is slidable forwards and rearwards of the machine, is employed and such pair of sliding tables are driven to slide at a same time under a control using a NC (numerical control) apparatus so as to slide a work table diagonally. However, this structure requires a pair of feed motors for driving the pair of sliding tables and two sets of feed mechanisms disposed between respective tables and motors so that such structure can hardly be said to be more inexpensive than the conventional structure comprising a parallel link mechanism. Further, because diagonal sliding movement of a work table is attained by independently driving two sliding tables, it is not assured that the work table crosses or passes a center of the machine during such diagonal sliding movement. Consequently, there remains a problem in accuracy of gear finishing.
Accordingly, a primary object of the present invention is to provide a novel table sliding apparatus for gear finishing machines in which combination of a pair of sliding tables is employed in a fashion such that diagonal sliding movement is attained by a single feed motor so as to eliminate problems set forth above.